code: def test_zeros(self, Source):
      source = Source()
      _, _, extent = source.single_tile(0, 50)
      assert extent == (0, 1, 50, 51)
  
file_path: cartopy/lib/cartopy/tests/io/test_srtm.py
imports: import numpy
  from numpy.testing import assert_array_equal
  import pytest
  import cartopy.crs
  import cartopy.io.srtm
  from .test_downloaders import download_to_temp
label_desc: Use image node_id 3 for calling the TestSRTMSource__single_tile obj's underlying member method code with example usage: obj.test_zeros(Source) without return types